<!DOCTYPE html>
<html>

<head lang="en">
    <meta charset="UTF-8">
    <title>银行业务查询</title>
</head>

<body>
    <script>
    ？ //补充代码
    function prom() {
        var a = prompt("请输入要查询的业务编号","");
        switch (a) {
            case 1:
                console, log("账户余额");
                break;
            case 2:
                console, log("转账余额");
                break;
            case 3:
                console, log("xinyonged");
                break;
            default:
                console.log("退出银行系统")
        }
    }
    </script>
</body>

</html>